February 2012

The three-part storm that I was expecting to be a two-parter. First, the snow in central MD over-performed Friday night as temperatures were just cool enough to allow snow to accumulate more quickly. The second part, the squall line, went as expected as accumulations of a dusting to a quarter inch (possibly a half inch in a few spots) were reported from that.

The third part that was enhanced by the inverted trough is what really got me. That produced a good 1-2 inches of snow over a good portion of the Delmarva Peninsula and in extreme eastern VA.

Another major failure in the forecast came in eastern PA and NJ as the coastal low and associated precipitation did not come as close to the coast as I had anticipated. Instead, it took a track similar to what the GFS showed and limited most of eastern PA and NJ to under an inch of snow during the first part of the storm. I also missed some of the higher lake-effect totals in northeast OH and northwest PA.

Weighing in the fact that I missed big in some areas, did fairly well in the mountains and the difficulty of the forecast, this was a D+.

Above normal boundary layer temperatures are going to hurt totals again for those east of the mountains. The main batch of precipitation will work through tonight and will start off as rain. It should change over to snow by the early morning hours in the DC/MD region, but it will take longer to try to accumulate (if at all). A quick burst of snow is expected in the region during Saturday afternoon/evening as the upper-level energy pushes through. This snow could accumulate up to about a half inch in spots (mostly south-central PA through most of MD and DC), but shouldn’t be much to worry about. Lake-effect and lake-enhanced snow will bring the higher 2-4 inch and 4-8 inch totals to the mountains.

The verification wasn’t as bad as I thought it would be. I still got the general idea right, but was off in some key areas east of the mountains. The northern extent of 1+ inch accumulation in NJ was a bit surprising, and the OH snow and southern WV/VA snow was a bit lacking compared to my forecast. The southern edge did go down along the mountain ridges a bit more than I expected.

I’m going to give myself another B- for this event. I bit into the hype east of the mountains in VA/MD and put the one inch line further south than I felt comfortable doing, and that backfired. Going conservative is definitely the best option with the snowfall forecasts this winter.

Plenty of cold air aloft, but surface temperatures look to hurt the initial snowfall accumulations before either the rates get high enough of the surface temperature cools to the freezing mark. Higher elevations stand a better chance of snow (both for surface temperatures and for snow ratios).

The verification on this one was rather interesting… some odd shapes/placements of the snow totals:

The front-end of the system over-produced and the back edge under-produced, with some front-end banding boosting totals in central MD. Lighter rates and above-freezing temperatures kept the totals down elsewhere. Overall, I had the right idea, but with a warm boundary layer and a weak system it’s always difficult to nail the accumulations. I’d give this forecast a B- for getting the general theme right within the oddly-placed snow totals.